Fatty River (ファッティ,Fatty River?) was a bounty hunter and an old friend of Jet Black. True to his nickname, he was a large man.
River tracked a bounty head, Giraffe, to a nightclub where he ran into Jet, who was also after Giraffe. Jet got into a boisterous conversation with him in order to keep River occupied while Spike followed Giraffe. Giraffe, however, was killed later, making the bounty disappear.
River later was taken out to lunch by Jet for information about Giraffe and Zebra, and he told him about their separation ten years prior, since there was no bounty in it.